Soluble or crosslinked graft copolymers of lignin acrylamide and hydroxylmethacrylate

ABSTRACT

A soluble or crosslinked graft copolymer of lignin-(2-propenamide)-(2-methyl-3-oxo-4-oxyhex-1-ene-6-ol) having a central lignin network and at least one grafted side chain, R, having randomly repeating units of the formula: ##STR1## such that the central lignin network has a molecular weight of about 1,000 to 150,000 and the total number of randomly repeating units in the grafted side chain or chains is in the range of 1 to 300,000, such that the total copolymer molecular weight is in the range of 1,000 to 30,000,000 for use as thickeners for water and aqueous solutions and may be advantageously used in the recovery of oil from subterranean wells, in the preparation and use of drilling fluid compositions, or in plastics and elastomers.

This invention was made with government support underCBT-84-17876/CBT-86-96158 awarded by the National Science Foundation.The government has certain rights in this invention.

REFERENCE TO CO-PENDING APPLICATION

This is a divisional application of co-pending U.S. patent applicationSer. No. 07/408,742, filed on Sept. 18, 1989 pending which was adivision of Ser. No. 07/287,000, filed on Dec. 20, 1988 and issued onDec. 26, 1989 as U.S. Pat. No. 4,889,902.

FIELD OF THE INVENTION

The present invention relates to soluble or crosslinked graft copolymersof lignin-(2-propenamide)-(2-methyl-3-oxo-4-oxyhex-1-ene-6-ol), methodsof making the same and uses therefor.

BACKGROUND OF THE INVENTION

Aqueous solutions which flow at a controlled rate under a given shearstress are required throughout a variety of industrial applications.Such control of viscosity of water is achieved by adding to water agentssuch as clays, large amounts of polar organic compounds such aspolyacrylates or high concentrations of salts. With the appropriateadditives, these aqueous solutions can suspend large amounts of a solidphase and form a thermodynamically stable mixture. These aqueoussolutions suspend finely divided solids and will flow slowly whenexposed to shear stress. Such solutions, free of solids, also flow moreuniformly in situations where numerous paths providing differentresistances to flow are open to the fluids. There are, however, numerousapplications for polymers in the dry state. Most water soluble polymersare not useful as plastic solids or in the dry state. This invention isdirected to materials that are so useful.

Each of the conventional agents mentioned above as useful in controllingfluid flow has attendant disadvantages, particularly when used torecover oil from subterranean wells. Hence, a need continues to existfor new agents which are capable of suitably thickening water andaqueous solutions having the desirable properties outlined below butwhich are free of attendant disadvantages. Further, many materials areused to make objects of manufacture with functional strength andresistance properties. These materials are usually not, however,polymers which can be dissolved in water. Further, most of these objectsare made from expensive synthetic chemicals rather than cheaper naturalcompounds like lignin. Objects of manufacture which contain largeamounts of lignin are desirable, inexpensive products because of low rawmaterials cost.

SUMMARY OF THE INVENTION

A soluble or crosslinked graft copolymer oflignin-(2-propenamide)-(2-methyl-3-oxo-4-oxyhex-1-ene-6-ol) having acentral lignin network and at least one grafted side chain, R, havingrandomly repeating units of the formulas: ##STR2## such that the centrallignin network has a molecular weight of about 1,000 to 150,000 and thetotal number of random units in the grafted side chain or chains is inthe range of 1 to 300,000 units, such that the total copolymer molecularweight is in the range of 1,000 to 30,000,000.

Objects, features and advantages of the present invention are to providean uncharged lignin graft copolymer; provide simplistic and reliableprocesses for preparing such lignin graft copolymer; provide a methodfor using an uncharged lignin graft copolymer in preparing highlyviscous, water-based foams or foams which are particularly useful in oilrecovery from subterranean wells; provide a method of boosting orenhancing polymer molecular weights during polymerization reactions;provide inexpensive plastics and articles of manufacture from lignin;and to provide gels of lignin for use as membranes, immobilizing fluidsor solids, and absorbing fluids.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In accordance with the present invention, there is provided a highmolecular weight graft copolymer containing lignin as the backbonenetwork and poly((1-amidoethylene)-co-(1-methyl-1-(1-oxo-2-oxybut-4-ol-1-yl)ethylene))as the grafted side chain.

Lignin is derived from woody plants. In fact, after cellulose, it is theprincipal constituent of the woody structure of higher plants. Lignin,which makes up about 25% of the weight of dry wood, acts as a cementingagent to bind the matrix of cellulose fibers together into a rigid woodystructure. See Biochemistry by A. L. Lehninger (Worth Publishers, 1970).

Moreover, lignin sources are abundant. Although the wood and bark wastefrom the lumber industry and wastes from agricultural operations couldprovide extremely large quantities of lignin, perhaps the mostaccessible, albeit smaller, source is the pulp and paper industry. Forexample, for 1978, it has been estimated that the U.S. chemical-pulpindustry produced 1.55×10⁷ metric tons of alkali lignin and 1.6×10⁶ tonsof lignosulfonic acids. See Encyclopedia of Chemical Technology, vol. 14(Kirk-Othmer, 1981).

In general, the molecular structure of the repeating lignin units andthe appropriate numbering thereof is as follows: ##STR3##

Lignin, regardless of origin, in general, is a complex oxyphenylpropenepolymer. In the natural state, lignin is a highly branched and partiallycrosslinked polymer. However, there appears to be some structuralvariation in branching depending upon whether the lignin is derived fromconiferous or deciduous species or from bark, cambium, sapwood orheartwood. During recovery, the lignin is chemically altered and isavailable in relatively pure form as a derivative having a molecularweight of about 1,000 to 150,000. Suitable lignins which may be usedaccording to the present invention are alkali lignins, HCI lignins,milled wood lignins (MWL) and 1,4-dioxane lignins, for example.

Alkali lignins are used in the examples of this application. However,reactions can be run on solvent-extracted lignin, kraft lignin, pinelignin, aspen lignin and steamexploded lignin. Alkali lignins are tan,brown or black powders. When free of metal cations such as sodium orpotassium, alkali lignins are water-soluble materials and are commonlycalled "free acid" or "acid free" lignin. When containing metal cations,such as sodium or potassium, the alkali lignins are slightly watersoluble materials which increase in water solubility as the pH increasesfrom 7 toward 14 and become completely soluble in 5 wt % aqueous sodiumhydroxide solutions. Alkali lignins have, as a basic repeating unit, theoxyphenylpropyl unit: ##STR4##

The aromatic ring is often alkoxy substituted, as shown, and the propenegroup often has a hydroxyl group attached in place of one hydrogen.Alkyl groups appear on some of the aromatic groups of the polymer andsulfur may be chemically bound to parts of the polymer, though few, ifany, sulfonate groups occur.

Bonding between repeat units in alkali lignin is complex and involvescarbon-carbon bonds between aromatic and/or alkyl carbons as well asether bonds between aromatic and/or alkyl carbons. Labile hydrogensexist in the material and may be replaced by metal cations, such assodium, potassium, calcium, or ammonium ions, to form alkali ligninsalts. Alkali lignins are readily identified by method of production andare a familiar class of compounds to those versed in the paper makingart.

In accordance with the present invention, to the lignin macromolecule,possibly to the aromatic ring of the oxyphenylpropene moiety, is graftedrepeating units of 1-amidoethylene: ##STR5## in combination withrepeating units of 1-methyl-1-(1-oxo-2-oxybut-4-ol-1-yl)ethylene:##STR6##

For example, when using alkali lignins in accordance with the presentinvention, a lignin graft copolymer of the following formula isproduced: ##STR7##

In this structural formula, the subscripts m and n are used to show thatlarge numbers of these repeat units can be attached to the ligninbackbone but the formula does not mean that these repeat units occur instrings of one type followed by strings of another type. Usually, thegraft copolymers formed have random copolymer side chains with the tworepeat units occurring in random sequence in the chain.

The preparation of this copolymer is accomplished, in general, underoxygen-free conditions by adding a redox initiator; a chloride salt,2-propenamide, ##STR8## and 2-methyl-3-oxo-4-oxyhex-1-ene-6-ol, ##STR9##to a lignin dispersion in a suitable solvent and allowing time for graftpolymerization to occur.

Preparation of alkalilignin-(2-propenamide)-(2-methyl-3-oxo-4-oxyhex-1-ene-6-ol) graftcopolymer in dimethylsulfoxide, (CH₃)₂ SO, will now be illustrated for asample composed of between 0.32 and 3.0 weight percent lignin, 0.2 and7.6 weight percent 2-propenamide, 0.2 and 7.9 weight percent2-methyl-3-oxo-4-oxyhex-1-ene-6-ol, 0.6 to 15.3 weight percent calciumchloride, 0.0 to 6.1 weight percent aqueous solution of cerium (+IV),and 60 to 97 weight percent solvent.

Significant variation in reaction mixture composition is possible aswill be illustrated in the examples to follow. However, there is ageneric way to prepare the graft copolymer. This method will now bedescribed, generally.

As a suitable solvent for the graft copolymerization of the presentinvention, it should be noted that, in general, organic solvents areused and, of these, the polar, aprotic solvents are preferred.Particularly noteworthy are the solvents dimethyl sulfoxide (DMSO),dimethyl acetamide (DMAc), dimethyl formamide (DMF), 1,4-dioxane,1-methyl-2-pyrrolidianone and pyridine. Of course, mixtures of thesesolvents can also be used such as 50/50 (vol/vol) mixtures of DMSO and1,4-dioxane. However, it is also possible to use 50/50 (vol/vol)mixtures of one of the above solvents, such as DMSO, with water.

An aliquot of 20 mL of purified solvent is placed in a 125 mL conicalflask. Lignin and finely ground anhydrous calcium chloride are added tothe pure solvent and the mixture is stirred for about 20 minutes whilebeing bubbled with nitrogen. After 10 minutes of nitrogen saturation, ahydroperoxide such as hydrogen peroxide, 1,2-dioxy-3,3-dimethylbutane or2-hydroperoxy-1,4-dioxycyclohexane is added to the reaction mixture.This addition can be made by adding an aqueous solution of the peroxidefor safe handling or the peroxide can be added directly. Solid2-propenamide (Monomer I) and a nitrogen-saturated solution of2-methyl-3-oxo-4-oxyhex-1-ene-6-ol (Monomer II) in solvent are addedwhile nitrogen gas is bubbled into the mixture. After about 10 minutes,a sufficient volume of 0.05 M ceric sulfate in water may be added, theflask is sealed under nitrogen, and the slurry is stirred for 10 moreminutes. The reaction starts immediately. The flask contents will oftenthicken slowly but may even solidify into a precipitate-laden, viscousslurry.

The reaction flask is placed in a 30° C. bath and allowed to sit for twodays. The reaction is then terminated with 0.5 mL of 1 wt % ofhydroquinone in water. The reaction mixture is diluted with 100 mL ofwater and stirred until a uniform reaction product is precipitated byadding the dilute reaction mixture dropwise to 1 liter of 2-propanone orother suitable nonsolvent for the graft copolymer. The solid isrecovered from 2-propanone by filtration and dried under vacuum at 40°C. To obtain a higher purity product which is more readily soluble, thereaction product is recovered from nonsolvent by filtration andredissolved in water. The aqueous solution is dialyzed against purewater using a 3,500-upper-molecular-weight-permeable, dialysis membranefor several days. The aqueous solution containing the solid is thenfreeze-dried. For a crosslinked product, the recovery process is todialize the product against water to remove the reaction solvent andthen freeze dry the product.

It is preferred that all reagents used be of reagent grade purity butless pure materials may be used if they do not contain inhibitors forthe reaction. Other concentrations of cerium (+IV) ion solution in othernonreactive solvents can be used to add this reagent to the reactionand, indeed, this reagent is not necessary for the reaction. The 0.05 Mcerium (+IV) sulfate solution is stable and convenient to use, however.The concentration of the ceric sulfate solution used can vary from about0.01 M to 0.3 M. Other reagents that may be used in place of ceric ion(Ce⁴⁺) include vanadium (V⁺⁵) or manganese ions (Mn³⁺, Mn⁴⁺, Mn⁷⁺). Itis preferred that the metal salt be added as an aqueous solution. Thereaction can be run without adding cerium or other oxidizing metal ionsbut slightly higher yields and better solubility properties are obtainedwhen the oxidizing metal ion is added. The graft copolymer can and willbe produced if this reagent is not added to the synthesis mixture butproduct properties are improved by the addition of cerium (+4) solution.Other changes in this procedure, evident to those skilled in synthesisor chemical manufacture can be made. The graft copolymer can also beproduced by adding nitrogen-saturated 2-propenamide to the reactionmixture in another solvent.

Other hydroperoxides, such as inorganic hydroperoxides may be used inplace of the hydrogen peroxide listed above. The graft copolymerizationreaction can be conducted with or without stirring once the monomer andmetal salt have been dispersed in the reaction mixture. The reaction isallowed to proceed for 1 to 200 hours, with 48 hours being a typicalreaction time. It is preferred to terminate the copolymerization byaddition of a free radical scavenger such as hydroquinone.

The graft terpolymer is easily recovered from a liquid reaction mixture.If the reaction mixture is a gel or thick slurry, it can be madepourable by mixing therewith 1 to 3 times its volume of distilled ordeionized water under low shear conditions until a homogeneous, pourablesystem is formed. The reaction mixture is added to 2-20, preferably5-10, times its volume of a nonsolvent for the polymer, such as2-propanone. Preferably the nonsolvent is stirred vigorously so as toform a vortex and the copolymer solution is slowly drained directly intothe center of this vortex. The precipitated graft copolymer is thenremoved from the nonsolvent solution by filtration, washed withnonsolvent, filtered, and vacuum-dried to a constant weight. A purerproduct can be obtained by the dialysis-freeze drying process describedabove. If the reaction product is crosslinked, the product is dried toform a solid block of polymer.

The following examples illustrate certain embodiments of this inventionwherein parts and percentages are by weight and temperatures are incentigrade unless otherwise indicated. Indulin AT, a commercial ligninproduct of the Westvaco Corporation Chemicals Division, P.O. Box 5207,North Charleston, S.C. 29406 and Eastman reagent-grade 2-propenamidewere used in these syntheses. BM-903,2-methyl-3-oxo-4-oxyhex-1-ene-6-ol, was obtained from Rohm Tech, Inc.,195 Canal Street, Malden, MA 02148 as a sample of lot number 174291 andwas purified by distillation from over KOH before use. A typicaldistillation was done at 1.3 pascals nitrogen pressure with a pot chargeof 100 g of monomer, as received, and 0.029 g of KOH with monomerdistilled at 50° C. Dimethyl sulfoxide, of reagent grade, fromMallinckrodt Chemical Co. and anhydrous calcium chloride also therefromwere used in these examples. Ceric sulfate solution was prepared fromreagent grade ceric sulfate and distilled water. The hydroquinonesolution was 1 wt % hydroquinone in distilled water.

The limiting viscosity number of the product in pure water wasdetermined using the Fuoss equation (a) to extrapolate several viscositymeasurements to zero polymer concentration.

    C/η.sub.sp =1/[η]+Q.sub.f C.sup.1/2                (a)

Here η_(sp) =(η-η_(o))/η_(o), C is polymer concentration in g/dL, Q_(f)is a fitting constant, and [η] is limiting viscosity number. See J.Poly. Sci., 3,603-604 (1948).

The present invention will now be further illustrated by certainexamples and references which are provided for purposes of illustrationand are not intended to limit the present invention.

Yield was calculated from the formula: (g=grams)

EXAMPLES EXAMPLE 1

A total of 0.5 g of lignin and 0.5 g of calcium chloride were placed ina 125 mL erlenmeyer flask containing 12 mL of dimethylsulfoxide. Themixture was stir-bubbled with nitrogen (N₂) for about 10 minutes before0.85 mL of hydrogen peroxide solution (30% by weight), was added to thereaction mixture. N₂ was bubbled through the reaction mixture for about5 minutes, while 1.00 g of 2-propenamide (I) in 5. mL ofdimethylsulfoxide which had been saturated with N₂ for 10 minutes wasthen added. After about 2 minutes of stirring and N₂ bubbling, 3.32 g of2-propenamide (I) and 0.87 g of 2-methyl-3-oxo-4-oxyhex-1-ene-6-ol (II)in 10.0 mL of dimethylsulfoxide were added. This solution had beensaturated with N₂ for 10 minutes before addition to the reactionmixture. After about 5 minutes of stirring and bubbling N₂ through thereaction mixture, the flask was sealed and placed in a 30° C. bath for 2days. The mole ratio of monomer I to II in the reaction solution was 9to 1. The molecular weight of monomer I used was 71.08 g and that ofmonomer II was 130.1 g. The reaction was then terminated by adding 0.1 gof 1% hydroquinone and 100 mL of water thereto. The stirred reactionmixture was precipitated in 1 L of 2-propanone and recovered byfiltration. The recovered solid was dissolved in 100 mL of water anddialyzed against water for 3 days. The dilute reaction product in thedialysis tube was recovered by freeze drying and found to weigh 5.10 g.The product was labeled 19-95-1. Yield =89.63 wt %. The product of thisexample had a lignin content of 4.62 wt % and a nitrogen content of15.21 wt %.

EXAMPLE 2

A total of 3.01 g of I and 2.04 g of II was placed in a 10 mL ofdimethylsulfoxide and stirred until dissolved. This solution was labeled19-92-B. A sample labeled 19-92-C was prepared by mixing 1.01 g ofmonomer I with 5.5 mL of dimethylsulfoxide and was saturated with N₂ for10 minutes. A total of 0.5 g of lignin and 0.5 g of calcium chloridewere placed in a 125 mL erlenmeyer flask containing 12 mL ofdimethylsulfoxide, dissolved, and labeled 19-92-A. The mixture (92-A)was stir-bubbled with nitrogen (N₂) for about 10 minutes before 0.85 mLof hydrogen peroxide solution (30% by weight), was added to the reactionmixture. N₂ was bubbled through the reaction mixture for about 5 moreminutes before 92-C was added to the mixture (92-A) and, 1 minute later,92-B was then added. After about 5 minutes of stirring and bubbling N₂through the reaction mixture, the flask was sealed and placed in a 30°C. bath for 2 days. The mole ratio of monomer I to II in the reactionsolution was 78.3 to 21.7 or about 4 to 1. The reaction was thenterminated by adding 0.1 g of 1% hydroquinone and 100 mL of waterthereto. The stirred reaction mixture was precipitated in 1 L of2-propanone and recovered by filtration. The recovered solid wasdissolved in 100 mL of water and dialyzed against water for 3 days. Thedilute reaction product in the dialysis tube was recovered by freezedrying and found to weigh 3.79 g. Yield =60.4 wt %. The product waslabeled 19-92-3. The product of this example had a lignin content of10.47 wt %, a nitrogen content of 15.37 wt %.

EXAMPLE 3

A total of 0.5 g of lignin and 0.5 g of calcium chloride were placed ina 125 mL erlenmeyer flask containing 12 mL of dimethylsulfoxide. Themixture was stir-bubbled with nitrogen (N₂) for about 10 minutes before0.85 m of hydrogen peroxide solution (30% by weight), were added to thereaction mixture. N₂ was bubbled through the reaction mixture for about5 more minutes, while 0.75 g of 2-propenamide (I) in 5.5 mL ofdimethylsulfoxide which had been saturated with N₂ for 10 minutes wasthen added. After about 2 minutes of stirring and N₂ bubbling, 1.752 gof 2-propenamide (I) and 2.686 g of 2-methyl-3-oxo-4-oxyhex-1-ene-6-ol(II) in 10.0 mL of dimethylsulfoxide were added. This solution had beensaturated with N₂ for 10 minutes before addition to the reactionmixture. After about 5 minutes of stirring and bubbling N₂ through thereaction mixture, the flask was sealed and placed in a 30° C. bath for 2days. The mole ratio of monomer I to II in the reaction solution was 63to 37. The reaction was then terminated by adding 0.1 g of 1%hydroquinone and 100 mL of water thereto. The reaction mixture was spunin a Sowall RC2-B centrifuge for 33 minutes at 7000 rpm. The supernatewas poured off from the sediment from this centrifugation and the twosample parts were labeled: supernate =aqueous and sediment =organic. Therecovered aqueous phase was diluted with 100 mL of water and dialyzedagainst water for 3 days. The recovered organic phase was suspended in100 mL of water and dialyzed against water for 3 days. The dilutereaction product in the dialysis tubes was recovered by freeze dryingand found to weigh aqueous =2.73 g and organic =1.49 g. Total yield is5.69 g. The product was labeled 19-96-1. Yield =74.2 wt %. The productof this example had a lignin content of 17.94 wt % and a nitrogencontent of 4.84 wt %.

EXAMPLE 4

A total of 0.5 g of lignin and 0.5 g of calcium chloride were placed ina 125 mL erlenmeyer flask containing 12 mL of dimethylsulfoxide. Themixture was stir-bubbled with nitrogen (N₂) for about 10 minutes before0.85 mL of hydrogen peroxide solution (30% by weight), were added to thereaction mixture. N₂ was bubbled through the reaction mixture for about5 more minutes, while 0.65 g of 2-propenamide (I) in 5.5 mL ofdimethylsulfoxide which had been saturated with N₂ for 10 minutes wasthen added. After about 2 minutes of stirring and N₂ bubbling, 1.184 gof 2-propenamide (I) and 3.357 g of 2-methyl-3-oxo-4-oxyhex-1-ene-6-ol(II) in 10.0 mL of dimethylsulfoxide were added. This solution had beensaturated with N₂ for 10 minutes before addition to the reactionmixture. After about 5 minutes of stirring and bubbling N₂ through thereaction mixture, the flask was sealed and placed in a 30° C. bath for 2days. The mole ratio of monomer I to II in the reaction solution was 1to 1. The reaction was then terminated by adding 0.1 g of 1%hydroquinone and 100 mL of water thereto. The reaction mixture was spunin a Sowall RC2-B centrifuge for 33 minutes at 7000 rpm. The supernatewas poured off from the sediment from this centrifugation and the twosample parts were labeled: supernate =aqueous and sediment =organic. Therecovered aqueous phase was diluted in 100 mL of water and dialyzedagainst water for 3 days. The recovered organic phase was suspended in100 mL of water and dialyzed against water for 3 days. The dilutereaction product in the dialysis tubes was recovered by freeze dryingand found to weigh aqueous =2.14 g and organic =2.09 g. Total yield is5.75 g. The product was labelled 19-96-3. Yield =73.6 wt %. The productof this example had a lignin content of 6.67 wt % and a nitrogen contentof 6.22 wt. %.

Note that examples 1 to 4 show that this product can be made in yieldsabove 60 weight percent and with mole ratios of amide monomer tohydroxyl containing monomer of from 1 to 1 up to 9 to 1.

EXAMPLE 5

A total of 0.51 g of lignin and 0.50 g of calcium chloride were placedin a 125 mL erlenmeyer flask containing 12 mL of dimethylsulfoxide. Themixture was stir-bubbled with nitrogen (N₂) for about 10 minutes before0.85 mL of hydrogen peroxide solution (30% by weight), was added to thereaction mixture. N₂ was bubbled through the reaction mixture for about5 more minutes, while 0.33 g of 2-propenamide (I) i 5.5 mL ofdimethylsulfoxide which had been saturated with N₂ for 10 minutes wasthen added. After about 2 minutes of stirring and N₂ bubbling, 0.66 g of2-propenamide (I) and 4.20 g of 2-methyl-3-oxo-4-oxyhex-1-ene-6-ol (II)in 10.0 mL of dimethylsulfoxide were added. This solution had beensaturated with N₂ for 10 minutes before addition to the reactionmixture. After about 5 minutes of stirring and bubbling N₂ through thereaction mixture, the flask was sealed and placed in a 30° C. bath for 2days. The mole ratio of monomer I to II in the reaction solution was 3to 7. The reaction was then terminated by adding 1.0 g of 1%hydroquinone and 100 mL of water thereto. The reaction product was auniform, homogeneous mass which did not dissolve in 100 mL of water thatwas added to the flask. The reaction product was mixed using a magneticstirrer. After 9 days, the reaction product was still a uniform,gellotinous mass distinct from the water added when the reaction wasterminated. The banging of the magnetic stir bar on the side of theflask broke the side of the flask and the 100 mL of wash water was lost.The gel product was collected and tested for solubility in varioussolvents. The product was labeled 19-100-1. Yield was not determinedbecause the pure polymer product was never isolated. The product of thisexample had a nitrogen content of 1.41 wt %.

                  TABLE 1                                                         ______________________________________                                        Solubility of Product 19-100-1 in Various Solvents                            Solvent      Solubility δ                                                                              Observations*                                  ______________________________________                                        ortho-xylene insoluble  18     No Change                                      Tetrahydrofurane                                                                           insoluble  18.6   No Change                                      2-propanol   insoluble  20.3   No Change                                      acrylonitrile                                                                              insoluble  21.5   No Change                                      pyridine     insoluble  21.9   Much Swelling and                                                             Sample Distention                              1-methyl-2-pyrolidine                                                                      insoluble  23.1   Much Swelling and                                                             Sample Distention                              dimethylformamide                                                                          insoluble  24.8   Much Swelling and                                                             Sample Distention                              ethanol      insoluble  26     No Change                                      1,2-dihydroxyethane                                                                        insoluble  29     Much Swelling and                                                             Sample Distention                              ______________________________________                                         *These observations describe the sample after it sat in the solvent for 4     hours.                                                                   

The coheasive energy density data, .sup.δ, show that solvents with δ=21to 25 (J/cm³)^(1/2) are very effective in swelling these materials.However, the fact that these solvents did not dissolve the sample showsthat the product is crosslinked. These lignin graft elastomers occurwhen the monomer I to monomer II ratio exceeds 1 to 1. Note that thisreaction procedure produces a copolymer that has a much higher molecularweight than that produced with higher mole ratios of I to II (I=∞).

EXAMPLE 6

A total of 0.50 g of lignin and 0.50 g of calcium chloride were placedin a 125 mL erlenmeyer flask containing 12 mL of dimethylsulfoxide. Themixture was stir-bubbled with nitrogen (N₂) for about 10 minutes before0.85 mL of hydrogen peroxide solution (30% by weight), were added to thereaction mixture. N₂ was bubbled through the reaction mixture for about5 more minutes, while 0.10 g of 2-propenamide (I) in 5.5 mL ofdimethylsulfoxide which had been saturated with N₂ for 10 minutes wasthen added. After about 2 minutes of stirring and N₂ bubbling, 0.20 g of2-propenamide (I) and 4.894 g of 2-methyl-3-oxo-4-oxyhex-1-ene-6-ol (II)in 10.0 mL of dimethylsulfoxide were added. This solution had beensaturated with N₂ for 10 minutes before addition to the reactionmixture. After about 5 minutes of stirring and bubbling N₂ through thereaction mixture, the flask was sealed and placed in a 30° C. bath for 2days. The mole ratio of monomer I to II in the reaction solution was 1to 9. The reaction was then terminated by adding 1.0 g of 1%hydroquinone and 100 mL of water thereto. The reaction product was auniform, homogeneous mass which did not dissolve in 100 mL of water thatwas added to the flask. The reaction product was mixed using a magneticstirrer. After 9 days, the reaction product was still a uniform,gellotinous mass distinct from the water added when the reaction wasterminated. The dilute reaction extract in the 100 mL of wash water wasrecovered by freeze drying and found to weigh 0.12 g and the insolubleorganic phase weighed 4.89 g. The fact that the water did not dissolvethe sample shows that the product is crosslinked. The product waslabeled 19-100-3. Yield was 88.0 weight percent. The aqueous extract ofthis example had a nitrogen content of 1.21 wt %, and a lignin contentof 18.44 weight percent. The insoluble solid of this example had anitrogen content of 0.64 wt %.

EXAMPLE 7

A total of 0.51 g of lignin and 0.50 g of calcium chloride were placedin a 125 mL erlenmeyer flask containing 12 mL of dimethylsulfoxide. Themixture was stir-bubbled with nitrogen (N₂) for about 10 minutes before0.85 mL of hydrogen peroxide solution (30% by weight), were added to thereaction mixture. After about 2 minutes of stirring and N₂ bubbling,0.30 g of 2-propenamide (I) and 4.89 g of2-methyl-3-oxo-4-oxyhex-1-ene-6-ol (II) in 15.5 mL of dimethylsulfoxidewere added. This solution had been saturated with N₂ for 10 minutesbefore addition to the reaction mixture. After about 5 minutes ofstirring and bubbling N₂ through the reaction mixture, the flask wassealed and placed in a 30° C. bath for 2 days. The mole ratio of monomerI to II in the reaction solution was 1 to 9. The reaction was thenterminated by adding 1.0 g of 1% hydroquinone and 100 mL of waterthereto. The reaction product was a uniform, homogeneous mass which didnot dissolve in 100 mL of water that was added to the flask. Thereaction product was mixed using a magnetic stirrer. After 9 days, thereaction product was still a uniform, gellotinous mass distinct from thewater added when the reaction was terminated. The dilute reactionextract in the 100 mL of wash water was recovered by freeze drying andfound to weigh 0.10 g and the insoluble organic phase weighed 4.02 g.The fact that the water did not dissolve the sample shows that theproduct is crosslinked. The product was labeled 19-102-1. Yield was 72.2weight percent. The freeze dried product of this example had a lignincontent of 22.47 wt % and a nitrogen content of 1.43 wt %. The insolubleproduct of this example had a nitrogen content of 0.37 wt %.

Examples 5 to 7 show that water insoluble plastics can be formed by theabove described method. When the mole ratio of amide monomer to hydroxylcontaining monomer is numerically less than 1 (1/1), the resultingpolymer is a plastic which is insoluble in water and other solvents.This unique behavior as a function of monomer ratio in the reactionmixture allows this new compound to be used to make solid objects andarticles of manufacture. It also allows these high-lignin content solidsto be used to make gelled (solvent-swollen) networks for application inmembranes, immobilizers, and fluid absorbers.

As already noted, the grafted side chain or chains are made of randomunits of 2-propenamide and 2-methyl-3-oxo-4-oxyhex-1-ene-6-ol. Moreover,the actual content of the grafted side chain or chains depends upon themolar ratio of monomer reactants employed. According to the presentinvention, it is acceptable to use from about 0.25 molar % to 99 molar %of 2-propenamide to about 99.75 molar % to 0.25 molar % of2-methyl-3-oxo-4-oxyhex-1-ene-6-ol. However, it is preferable to use amolar % in the range of 5 to 95 or 95 to 5, respectively. The graftedside chain or chains appear to attach at one or more of the 2-, 5- or 6-aromatic ring positions on the oxyphenylpropene moiety. Of course theprecise content of the grafted side chain or chains depends upon thecontemplated use. For example, in uses where water solubility isrequired, more of the 2-propenamide monomer should be used. Conversely,where less water solubility and more plastic or elastomer character isdesired, more of the 2-methyl-3-oxo-4-oxyhex-1-ene-6-ol monomer shouldbe used.

Although the polymerization reaction of the present invention is afree-radical polymerization, the scope of the present invention clearlyextends the concept of gel-state reactions to other types ofpolymerization reactions such as ionic or step polymerizations.

The soluble or crosslinked lignin graft copolymers of the presentinvention can also be used advantageously in a conventional manner forthe enhanced recovery of oil in subterranean wells. Typically in suchprocesses, the graft copolymer is dispersed or solubilized in injectionwater, the water may then be injected into the subterranean formation,and the injected water is then moved through the formation acting as ahydraulic ram, thereby pushing the resident oil to a production well.However, the particular chemistry of materials of the present inventionmakes for a much more economical method of oil production. If the oil ispushed to a production well by an air-aqueous foam, the cost of thepushing agent is much lower and the oil is recovered at much lower cost.The complex polymers of the present invention are particularly suited toforming such a foam, as shown by the following example.

EXAMPLE 8

A glass column, 1.22 meters tall and 2.8 cm in internal diameter, wasmounted vertically with a single hole, rubber stopper in the bottom ofthe column. The single hole of the rubber stopper was sealed with aglass capillary through which nitrogen gas could be introduced to thecolumn. Nitrogen was bubbled into the column at a rate of 21.6 mL of drygas per second, measured at 24° C. and 1 atmosphere pressure. A 0.26gram sample of the product of example 2 was introduced into 49.75 g ofdistilled water and dissolved by rapid stirring. This solution, whenintroduced into the column apparatus described above made a 7.5 cm highblock of fluid above the nitrogen inlet at the bottom of the column. In60 seconds of bubbling, the fluid had produced stable foam bubbles whichhad risen up the column to a total height of 39 cm above the surface ofthe fluid in the column. The column was then cleaned and refilled withwater. In 60 seconds of bubbling, the distilled water had produced foambubbles which had risen up the column to a total height of 2 cm abovethe surface of the fluid in the column. The addition of 0.52 weightpercent copolymer to the water had increased its capacity to formbubbles, useful in foam flooding of an oil-bearing formation, 20 fold.It is noted that the particular amounts and composition of the presentlignin graft copolymer effective for such use as well as otherparticulars of this use would be within the knowledge of one skilled inthe art having read the present disclosure.

The molecular weight of the water-soluble lignin copolymers of thepresent invention are in the range of about 1,000 to about 30,000,000 asdetermined by size exclusion chromatography using known techniques.Under the process conditions of the present invention already described,it is possible to obtain molecular weights of about 40,000 to 300,000.Under these conditions, the polymer molecular weight is generallyincreased by increasing the ratio of moles of monomer to moles ofhydroperoxide. The converse is true when diminishing the molecularweight.

In general, the reaction occurs at room temperature without adding heat.Reaction times are somewhat variable and on the order of from 1 to about48 hours with reaction yields as high as 80 weight percent possible inabout 1 hour. The preferred reaction time in a commercial or continuousprocess of manufacture of the copolymer is 1 to 2 hours. Although thepolymerization reaction of the present invention is a free-radicalpolymerization, the scope of the present invention clearly extends theconcept of grafting reactions to other types of polymerization reactionssuch as ionic or chain polymerizations.

Having now fully described this invention, it will be apparent to one ofordinary skill in the art that many changes and modifications can bemade thereto without departing from the spirit or scope of the inventionas set forth herein

I claim:
 1. A method for preparing a copolymer of lignin which comprisesthe step of free radically graft copolymerizing 2-propenamide and2-methyl-3-oxo-4-oxyhex-1-ene-6-ol on lignin.
 2. A method as called forin claim 1, wherein said step of copolymerizing comprises:a) adding ahydroperoxide to a solvent; and b) adding lignin, a chloride-containingsalt, 2-propenamide and 2-methyl-3-oxo-4-oxyhex-1-ene-6-ol, therebyinitiating free radical polymerization.
 3. The method as called for inclaim 2, wherein said lignin and chloride-containing salt are added tosaid hydroperoxide in a solvent, and then said 2-propenamide and2-methyl-3-oxo-4-oxyhex-1-ene-6-ol, are added.
 4. A method as called forin claim 3 further comprising adding an aqueous solution of at least oneion selected from the group consisting of ceric, vanadium and manganeseions.
 5. The method set forth in claim 4, wherein the step ofcopolymerizing is conducted so as to produce a composition whichcomprises about 0.32 to about 3.0 weight percent lignin, about 0.2 toabout 7.6 weight percent 2-propenamide, about 0.2 to about 7.9 weightpercent 2-methyl-3-oxo-4-oxyhex-1-ene-6-ol, about 0.0 to 6.1 weightpercent aqueous solution of cerium, and about 60 to 97 weight percentsolvent.
 6. The method according to claim 5, wherein said hydroperoxideis selected from the group consisting of t-butyl hydroperoxide andhydrogen peroxide.
 7. The method according to claim 1, whereinhydroperoxides are added to lignin and chloride-containing salt, thenthe 2-propenamide and 2-methyl-3-oxo-4-oxyhex-1-ene-6-ol are added tothe lignin mixture.
 8. A method of increasing the molecular weight oflignin during polymerization which comprises effecting saidpolymerization in a reaction mixture containing a mole ratio of2-propenamide to 2-methyl-3-oxo-4-oxyhex-1-ene-6-ol of not greater than1 to
 1. 9. The method of claim 8, wherein said polymerization is afree-radical polymerization.
 10. The method according to claim 9,wherein said molecular weight is increased to a molecular weight in therange about 1,000 to about 30,000,000.
 11. The method according to claim8, wherein said reaction occurs at about room temperature.
 12. Themethod according to claim 9, wherein said free radical reaction is afree radical graft copolymerization of 2-propenamide and2-methyl-3-oxo-4-oxyhex-1-ene-6-ol on lignin.